Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$146.66	8.131%	$158.5849	$158.58	$158.60	$158.60
Purchase #2	$103.86	7.692%	$111.8489	$111.85	$111.85	$111.80
Purchase #3	$202.55	4.854%	$212.3818	$212.38	$212.40	$212.40
Purchase #4	$36.74	10.816%	$40.7138	$40.71	$40.70	$40.70
Purchase #5	$239.56	13.164%	$271.0957	$271.10	$271.10	$271.10
Purchase #6	$91.66	5.347%	$96.5611	$96.56	$96.55	$96.60
Purchase #7	$67.80	6.605%	$72.2782	$72.28	$72.30	$72.30
7 purchase totals =	$888.83		$963.4644	$963.46	$963.50	$963.50